Thin Walls
by MaybeThere'sHope
Summary: Remember how Jace used to hear Maryse sing to Alec through the wall? Well, he can still hear through it. Just...not something as innocent as singing anymore. Malec. A little OOC, so don't say I didn't warn you. M/M, Lemon, Naughty. :


**Okie dokie guys, this was just a random idea I had and just had to get down on paper. OOC ALERT. Just warning you now. This is not in the Misery Loves Glamour AU, obviously. It is back in TMI world hehe. (I know it's been a while lol).**

**I hope you guys like it and as always, thanks to StarryOwlEyes for fixing my booboo's. **

**I do not own these wonderful characters. Cassie does. I just make them do naughty things.**

Jace and Clary crept through the halls of the institute like silent cats. Their hearing was magnified, like that of all teenagers who are sneaking around doing things they shouldn't do. They tended to jump at every little sound (which was out of character, especially for Jace). But really, your average demon had _nothing_ on Maryse Lightwood when she had her Mom Swag on. If she caught the two of them sneaking to Jace's room at 1 in the morning, they'd be flayed alive. Or, at least, Jocelyn would be called, and Clary retrieved in a matter of minutes. Jace would probably be stuck cleaning the toilets of every bathroom in every spare bedroom of the entire Institute, but something told them it was worth it, so they took the chance.

They hadn't actually done the deed yet, but Jace was working his way towards it. Getting Clary to sneak out of her house, and take a cab all the way to Manhattan was a step in the right direction at least. As they came to his room, he gingerly opened the door. Both of them cringed at the slight creaking sound it made, thinking it would be their doom. However, they listened up, and down the hall for a few seconds- all was well. They slipped inside, and Jace locked the door quickly and quietly. He turned to Clary, capturing her lips, and scooping her up in one swift movement as she wrapped her legs around him. He walked over to the bed, and deposited them both onto the mattress.

"Oh my GOD we are so going to get caught for this," Clary giggled, not seeming to care in the least at the moment. They attacked each other's lips with hungry kisses rolling around, attempting to shed clothing, and get under the covers. Clary did insist on remaining in her underwear, though. But, at least Jace had rid her of clothes. He was happy. Then, he remembered something.

"Oh, by the way, I should probably let you know that Magnus' apartment is being renovated," Jace said as they lay side by side, his fingers playing with her bare shoulder, causing her to shiver slightly.

"Uh, what does that have to do with anything?" she asked, completely puzzled.

"Well, Alec usually stays over there all the time now, but for the last couple of weeks, he's been in his old room here," Jace replied.

"Isn't that his privilege? I mean, he still technically _lives_ here, right?"

"I think Maryse pretty much says he's 18, and can do what he wants, but I highly doubt she agrees with their…activities…happening under her roof. I mean, I guess she thinks what they do at Magnus' apartment is all well and good, but her baby boy acting like a hussy down the hallway from her isn't what she'd call acceptable."

"Jace, what _kind_ of activities, exactly?" Clary was wondering.

"Oh, you'll find out. Actually, it's a little past one now. I give it about half an hour." However, his estimation was incorrect. No sooner had he uttered the sentence than they heard a loud thud against the wall behind them, the one that Jace's room shared with Alec's. Jace sighed heavily, turning on his back. "And so, it begins," he said.

Clary, on the other hand, was propped up on her elbow, wondering what in the hell that sound was. She listened intently, trying to catch the faint sounds she could hear through the wall. She heard clanking sounds, like something was hitting the metal headboard. Then she started to hear words.

"_Stay_," said a voice. Unmistakably Magnus, it made her shiver, but not in fear oddly enough. What were they doing? In response, she heard a low whimper. Definitely Alec. But, he was sounding very…anxious. Was that the right word?

"Clary, seriously. Don't _try_ to listen. Trust me, you won't have to," said Jace, still staring up at the ceiling, and speaking broodingly. She almost questioned his tone, but put it off because then she heard something very loud.

A sharp _crack!_ echoed through the wall, followed by a loud moan that was clearly let out through a bitten lip. Another resounding _smack!_ came through, again causing a moan that was louder than the first.

"_Angel_, what is going on?" Clary said out loud to herself.

"Babe, if only you weren't so naïve," Jace answered her.

Clary was about to protest, but then she heard another loud smack and an "Oh GOD!" which sounded like it was screamed directly at the wall. What was happening in there? Alec sounded like he was in pain or…something. A continuance of sharp cracking sounds was followed by more, and more litany-esque cries, each one sounding more and more ecstatic. Okay, Alec seemed to be enjoying himself at least. She kept listening.

"Fuuuuuuck, AGAIN!" he whined. Another smack.

"You like it, dirty whore?"

"Dear GOD, Jace," Clary whispered in rapture. "This is hot!"

"By the Angel, no. No. Just…no." Jace cringed as Alec's pleasure-racked moan resounded through the wall again.

"What's your problem?" Clary asked, calling him out on his tone from earlier.

"Well, obviously, he's getting _laid. _And, if you haven't noticed, the circumstances are quite different in _this_ bedroom. Although you seem to be turned on, and willing. I just can't win."

"I don't think he's getting laid, Jace. At least, not yet," she giggled. She could only imagine what was actually going on. It was probably something innocent as hell, and they were just making it out to be some big deal. Jace was probably just imagining things every night, wishing he were getting some. She actually couldn't blame him. But seriously, they couldn't be doing anything horribly sexual in there, could they? Jace was right; Maryse would have been in there already, threatening Magnus for stealing her son's virtue. Definitely, they were just doing something innocent.

* * *

><p>Magnus stepped back, and admired his handiwork. Alec's ass was a ripe strawberry color, and it even had little places on the sides where the shape of Magnus' fingers could be made out. It was absolutely delicious looking. He couldn't wait to devour the gorgeous sight in front of him.<p>

Alexander Lightwood, shyboy extraordinaire was currently handcuffed (using two sets, obviously, to pull his arms to opposite corners) to his own headboard, face down. His ankles were secured in much the same way with scarves Magnus had conjured up at the last minute. Alec had agreed to the cuffs, but he'd said that was where it stopped. Ha! Magnus waited till his hands were secure then pried his legs apart and given them the same treatment while Alec whimpered in half-hearted protest. Magnus _knew_ he'd like it, that little filthy hussy. This position had many advantages: first of all, Alec was in complete and utter submission, laying there in wait to be ravished. Secondly, and almost just as hot, was the fact that every time he screamed out Magnus' name, or some kind of curse or prayer to the Angel, he screamed it straight at the wall. Magnus chuckled.

Though Alec was completely bare skinned, Magnus still needed to peel off his skin-tight black jeans. His cock was straining against the denim and it was getting decidedly uncomfortable. He knew Alec was ready to get started, the way his ass was squirming on the bed, trying to get enough friction on his own erection. It was simply mouthwatering. Magnus grabbed a bottle of lube from the bedside table, and made his naked way to the bed. Once his first three fingers were coated good, and slick; he used his free hand to grasp Alec's left cheek firmly, causing the Shadowhunter to jump in anticipation. Magnus wasted no time, pulling him apart, and shoving two fingers in. They'd been going at it like rainbow rabbits for the past week, and a half, so Alec was pretty loosened up anyway. As soon as Magnus was down to the knuckles, he curled his fingers just so.

"BY THE ANGEL MAGNUS! GOD!" Oh, that was music to Magnus' ears. He could only imagine what their next-door neighbors were thinking. He'd heard Jace, the little bastard, sneaking Clary in about half an hour ago. He wondered what she thought of their free gay porn audio. Magnus sure as fuck loved it.

He started to pump his fingers in, and out quicky, adding the third after a few minutes. Alec's moans, and sighs became louder with each thrust of his hand. And before long, Magnus couldn't stand it anymore. He situated himself between Alec's spread eagle position, giving him one more playfully forceful smack on the ass, listening to the beautiful whimper that it pulled from his boyfriend. It was so hot, having a Shadowhunter in his grips like this. But it was even better that it was shy-outside-the-bedroom Alec. He leaned over, positioning himself, and letting the head work its way in just a tiny bit.

"You ready, sweetness?" he whispered into Alec's ear, biting it for good measure.

"Uh huh," came Alec's strangled reply from his face that was buried in the pillows. That was all Magnus needed. He thrust in to the hilt hard, and fast.

* * *

><p>All of a sudden, Clary heard a scream. "UUUUNNNNNNNNGGGG! Ah…Ah…AH…" and it just kept going. Alec's pants, and moans of ecstasy were keeping time with the steady thudding on the wall. She wondered if the headboard would be compromised soon.<p>

"My lord, they're going to break something in there," she mused.

"Nah. It's been good since they started staying here. It's holding up fine, trust me."

As the minutes passed, Alec's strangled, staccato cries were getting higher, and higher in pitch. Clary couldn't deny, it was damn sexy to listen to. She was getting a little hot, and bothered by the whole thing. Also, she was getting increasingly jealous of Alec. She and Jace had decided to wait—but still. A girl had needs that could be met in other ways besides sex. She was brought out of her brooding fantasizing by Jace speaking again.

"One time, they went at it for three straight hours," he said.

"_Really_?" she asked, impressed.

"Yeah. Seriously, I commend Magnus. Warlocks must have some spell up their sleeves for that stuff. Just, don't ever expect me to have stamina like that."

"You commend Magnus? I commend _Alec_," she said, eyes wide.

Jace raised and lowered his eyebrows in thought. "Touché," he replied. And then, the real noise started. Clary was dumbfounded that Maryse hadn't come busting through next door, considering it sounded like Alec was being exquisitely murdered in the next room. Clary was still incredibly jealous.

Alec's strangled moans and cries were so loud and ecstatic they were hard to listen to. Clary was admittedly incredibly aroused. Jace just lay there, staring at the ceiling, brooding in silence until it was over.

"Magnus! Mmmph! Ah! Unf! Uh huh! Yes! Yes! Yeah! Yeah! Yeah! Unnnngh GOD! Uhhhh!" The pounding went on, getting more rapid by the second. Clary began biting her lip without even knowing it, just to keep quiet.

"So. Un. Fair." Jace said to himself. As he uttered the last word, there was a loud resounding _FUUUUUUUUUUCK_ that went muffled by the end. Clary knew Alec had buried his face in the pillow. She didn't know why; he'd already woken the dead. There was extreme heavy breathing, followed by the clanking noise again. _Innocent, my ass_, she thought to herself with a smile.

Into the silence that followed, Clary couldn't help but wonder out loud, "I never would have pegged Alec to be a screamer."

"Me either. I don't think he even knows we can hear him. He'd never face me at the breakfast table if he did," Jace said with a small smile. "Although, judging by the ridiculous shit-eating grin Magnus wears every morning when he walks out of here, I'm almost positive he knows we do."

The next morning, they were doing just that. After Clary had slipped out around 4am to change, and come back at 8, they were gathered around the table in the kitchen. Maryse was preventing Isabelle from touching the eggs in the pan on the stove, Robert was gone already, and Magnus, Alec, Jace, and Clary were sitting in silence, just staring in different directions. There wasn't much to say during breakfast, not until their plates had been cleared, and Isabelle had gone up to her room. Maryse was helping Alec with the dishes across the room.

Jace leaned in to whisper, "You know, you guys are going to get caught someday. Can't you throw up a soundproof spell, or something?"

Magnus' expression didn't change. "I do. Every time," he replied, taking another sip of his green tea latte.

Jace huffed in annoyance. "Well, apparently it's not very good, because I hear absolutely everything."

Magnus just put his mug down and looked up to the sky, feigning the same nonchalance he always did. "Oh, my soundproofing is remarkable in its amazingness. I'm just a bastard, and leave it off the wall that connects with yours," he said, bringing his eyes down to stare into Jace's, and smirking. He then got up and went over to peck Alec on the cheek. "Later, sweetness." He winked as he passed back by the breakfast table. Jace was fuming, but all Clary could do was smirk while blushing, because she was kind of grateful to the warlock for giving her such great spank-bank material.

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